During the coming year studies will be carried out to determine the importance of protein sulfhydryl groups and carboxyl groups in the adsorption properties of plasma fibronectin and to determine whether there are specific domains of the fibronectin molecule that have high affinity for the material surface. To determine the importance of sulfhydryl groups, plasma fibronectin will be reduced and alkylated. To determine the importance of carboxyl groups, plasma fibronectin will be incubated with a carbodiimide in the presence of glycine methyl ester. Then experiments will be carried out to measure the various adsorption parameters of the modified fibronectins in relationship to those that have been established for normal fibronectin in the studies carried out during the past year. It will be of particular interest to determine whether there is still a cooperative effect and how resistant the modified fibronectins are to desorption by various reagents. Also, competition studies between modified and normal fibronectins will be carried out.